Unmarried couples which have failed to draw up a will could be sitting on a financial time-bomb that may see the survivor in a worst-case scenario end up penniless, with all of the deceased's estate passed to the taxman.

These warnings - which are increasingly pertinent at a time when more and more couples are co-habiting - come from Anne Elliott, a Partner at Darlington law firm Latimer Hinks.

"The value of your assets, how you own them as between yourselves, and by whom you are survived, can all affect how your estate is treated after your death," says Mrs Elliott.

"Writing a will is critical for people who are unmarried because if a partner dies without a will the estate passes to the next of kin i.e. blood relatives, and if there are none, potentially to the Crown."

"Although there are cases where joint ownership of assets can help the fact/effect of no will, your partner will have no right to your estate unless you have written a will in which he or she is named as the beneficiary."

"If you are unmarried and have no living blood relatives, your entire estate will pass to the taxman."

"Whilst this worst-case scenario is unlikely to happen in most cases, partners who satisfy certain criteria have claims against the estate. Having your wishes clearly written down will save your family a great deal of trouble and heartache to say nothing of expensive fees at what is inevitably a very difficult time emotionally."

Two out of three people in Britain die without leaving a will; many assuming that this does not matter because their spouse will automatically inherit their estate should they die.

Mrs Elliott highlights five good reasons to leave a will. Doing so allows you to:

• Choose your executors i.e. who will sort things out.
• Appoint guardians for your children.
• Provide sensibly for your spouse/partner.
• Ensure that your children do not receive their inheritance at the age of 18 unless you want them to.
• Potentially make significant savings on Inheritance Tax.